Mechanism to improve stent securement

Abstract

The present invention comprises a securement member to improve securement of a stent upon an expandable balloon and delivery catheter, and to constrain portions of the stent before and during stent deployment. Generally, the securement member comprises a securement connector arranged to engage a catheter, at least one flexible connecting member coupled to the securement connector, and a locking member arranged to engage a portion of a stent.

1. A device for preventing stent movement during delivery comprising:
 a securement connector arranged to engage an outer surface of a catheter; 
 at least one flexible connecting member made from a shape memory material, said flexible connecting member comprising a serpentine band, said shape memory material having an Af temperature lower than normal human body temperature, said at least one flexible connecting member being balloon expandable, said flexible connecting member having a first end portion and a second end portion, the first end portion coupled to said securement connector; and 
 a locking member located at said flexible connecting member second end portion arranged to engage a portion of a stent; 
 wherein a diameter of the securement connector remains constant during stent expansion. 
 
     
     
       2. The device of  claim 1 , further comprising a plurality of flexible connecting members. 
     
     
       3. The device of  claim 2 , wherein said flexible connecting members are arranged to expand with the stent. 
     
     
       4. In combination, the device of  claim 1  and a catheter, the catheter having a balloon with a stent disposed thereabout, the stent engaged to the device. 
     
     
       5. The combination of  claim 4  wherein the stein includes an engagable portion arranged to engage said looking member. 
     
     
       6. The combination of  claim 5  wherein the device is made of a shape memory material which is balloon expandable and which is programmed to return an unexpanded diameter following balloon expansion. 
     
     
       7. The device of  claim 1 , wherein the shape memory material comprises a shape polymer. 
     
     
       8. The device of  claim 1 , wherein the securement connector is fixedly attached to the catheter. 
     
     
       9. The device of  claim 1 , where the flexible connecting member comprises a length between the first end portion and the second end portion, and a point on the stent experiences radial displacement upon stent expansion, the length being greater than the radial displacement. 
     
     
       10. A device for preventing stent movement during delivery comprising:
 a securement connector arranged to engage an outer surface of a catheter; 
 a plurality of flexible comprising members, each of said flexible connecting members made from a shape memory material, each of said flexible connecting members having a first end portion and a second end portion, the first end portion coupled to said securement connector, wherein the flexible connecting members comprise a serpentine band; and 
 a locking member located on each of said flexible connecing members second end portion arranged to engage a portion of a stent in a way that allows freedom of movement in a radial direction between the locking member and the stent; 
 wherein a diameter of the securement connector remains constant during stent expansion. 
 
     
     
       11. The device of  claim 10 , wherein at least one of the flexible connecting members is balloon expandable. 
     
     
       12. The device of  claim 10 , wherein the shape memory material has an Af temperature lower than normal human body temperature. 
     
     
       13. A stent delivery system comprising:
 a catheter comprising an expandable balloon and a proximal shaft portion, the proximal shaft portion located proximal to said expandable balloon along the length of the catheter; 
 a radically expandable stent having at least one engagable portion; 
 at least one radically expandable constrainment member having a first end coupled to said catheter proximal shaft portion and a second end having at least one engaging portion; 
 wherein the at least one constrainment member is in the form of a serpentine shaped wherein said constrainment: member engaging portion and said stent engagable portion band and; 
 wherein said constrainment; member engaging portion and said stent engagable portion are engaged; 
 and wherein said constrainment member ingaging portion and said stent engagable portion may remain engaged throughout the expansion of said balloon. 
 
     
     
       14. The stent delivery system of  claim 13 , wherein said constrainment member engaging portion and said stent engagable portion are constructed and arranged to disengage when said balloon is deflated. 
     
     
       15. The stent delivery system of  claim 14 , wherein said constrainment member is made from a shape memory material. 
     
     
       16. A stent delivery system comprising:
 a catheter; 
 an expandable balloon; 
 a radially expandable stent having at least one engagable portion; 
 at least one radically expandable constrainment member having a first end coupled to said catheter and a second end having at least one engaging portion; 
 wherein said constrainment member engaging portion and said stout engagable portion are engaged and are constructed and arranged to remain engaged until said balloon is at least partially deflated; and 
 wherein the constrainment member is in the form of a serpentine shaped band: and 
 wherein the constrainment is made from a shape memory material and is programmed to return to a reduced diameter configuration following balloon expansion. 
 
     
     
       17. A stent delivery system comprising:
 a catheter comprising an expandable balloon and a proximal shaft portion, the proximal shaft portion located proximal to said expandable balloon along the length of the catheter; 
 a radially expandable stent having at least one expandable portion; 
 at least one radially expandable constrainment member having a first end coupled to said catheter proximal shaft portion and a second end having at least one engaging portion; 
 wherein said constrainment member ingaging portion and said stent engagable portion are engaged; and 
 wherein said constrainment member engaging portion and said stent engagable portion are in the form of a ball and socket: 
 and wherein said constrainment member engaging portion and said stent engagable portion may remain engaged throughout the expansion of said balloon. 
 
     
     
       18. A stent delivery system comprising:
 a catheter comprising an expandable balloon and a proximal shaft portion, the proximal shaft portion located proximal to said expandable balloon along the length of the catheter; 
 a radially expandable stent arranged about said expandable balloon in an unexpanded state, said stent having an end portion, said end portion having at least one engagable portion; 
 at least one radially expandable constrainment member arranged to partially overlay said balloon, said constrainment member having a first end coupled to said catheter proximal shaft portion, the constrainment member further comprising a serpentine band having a plurlality of openings therethrough and an engaging portion; 
 wherein said constrainment member engaging portion is arranged to engage said stent engagable portion; 
 and wherein when said constrainment member engaging portion and said stent engagable portion are engaged, movement of said stent engagable portion in the axial direction is prevented. 
 
     
     
       19. The stent delivery system of  claim 18 , wherein when said constrainment member engaging portion and said stent engagable portion are engaged, said stent engagable portion is further constrained from rotation about the catheter. 
     
     
       20. The stent delivery system of  claim 18 , wherein when said constrainment member engaging portion and said stent engagable portion are engaged, said stent engagable portion is free to move in the direction of radial expansion. 
     
     
       21. A device for preventing stent movement during delivery comprising:
 a securement connector arranged to engage an outer surface of a catheter; 
 at least one flexible connecting member made from a shape memory material, said flexible connecting member comprising a serpentine band, said flexible connecting member having a first end portion and a second end portion, the first end portion coupled to said securement connector; and 
 a locking member located at said flexible connecting member second end portion arranged to engage a portion of a stent; 
 wherein a diameter of the securement connector remains constant during stent expansion; and wherein the shape memory material comprises a shape memory alloy having an Austenite phase and a Martensite phase.